Larry, I know what you are talking about. I saw somebody here that had done what you suggested. He had the walls and supports up and had a rail that he nailed the roof panel to then put the spars on top of that. It worked real slick but was a little too advanced for me at the time. I'll try that on my next one. I went to HD this morning and got some more clamps and glued and clamped the problem panel and spar together.
Doug, you were right about the clamping part. It came down to where I can live with it. I also bought a 1/4" router bit for my Dremel tool and cut kerfs every inch for the panel that will butt up against the first one. I'm hoping that will help take the stress off of the spars. I should've done that with the first one but I GREATLY underestimated how hard it was going to bend 1/4" ply in a 24" radius!!
I'm really learning alot with this project. Now I need to figure out how to fix the wheel opening I goofed up this morning. It's really off

!!